Diversity And Niche Adaptation In Marine Cyanobacteria


Thursday, March 17, 2011
Redfield Auditorium - 12:00 Noon
Dr. Anton Post
Senior Scientist, Josephine Bay Paul Center, Marine Biology Laboratory

Forging a linkage between species (genotype) and functional diversity (ecotype) is one of the great challenges in the ecology of marine microbes. This challenge can be addressed to some extent from the study of nitrogen stress genes in marine picocyanobacteria. We employ the N-regulatory gene ntcA as molecular marker for phylogenetic analyses and study the NtcA regulon as an indicator of functional diversity. We will present data to show distinct Prochlorococcus ntcA clades in different ocean basins with novel clades for the Tropical Indian Ocean and the Antarctic Circumpolar Current.  Based on the clustering pattern and a GC content of 44-45% this latter clade was tentatively identified as a novel clade of low light adapted Prochlorococcus. On the assumption that gene composition of the NtcA-regulon reflects the complexity of N-nutrition in their immediate environment, we analyzed a 60 kB genomic region in marine Prochlorococcus and Synechococcus. that encodes for the main N-acquisition modules. Clade specific differences in nitrate, urea and cyanate utilization analyzed on environmental samples will be used to illustrate the constraints of ecotype definition based on a (still) low number of genome sequences for culture representatives of the various clades.